1. Technical Field
The present invention relates to a printed circuit board (PCB), and more particularly, to a PCB which includes an electromagnetic bandgap structure that is disposed around an antenna so as to prevent noise from being transmitted to the antenna.
2. Description of the Related Art
Recently, as a radio communication device is required to have a large number of different functions, the number of components mounted on the device has increased and the size and thickness of the device have been remarkably reduced, and thus the density of a PCB which is an important component of the device is on a continuously increasing trend.
When the density of the PCB is increased in this way, the distances separating the mounted components become reduced, and accordingly, signal interference occurs therebetween. A signal generated from a component has an influence in the form of noise on another adjacent component.
In particular, depending on an increase in the density of the PCB, a chip component which has been mounted around the antenna may be located nearby the antenna, so that a signal generated from the chip component affects the antenna, undesirably deteriorating performance of the antenna.
Generally, communication is achieved in such a manner that the antenna receives power from the feed line of a main PCB to thus radiate radio frequency to the outside.
In the case where the antenna is a FIFA or loop type antenna, the antenna simultaneously uses the ground and feed terminals of the main PCB. In this way, when the antenna simultaneously uses the ground and feed terminals of the main PCB, noise generated from the RF circuit or digital circuit of the main PCB propagates to the inside or outside of the PCB and thus affects a radio frequency output, consequently deteriorating performance of the antenna in the frequency band affected by noise.
Because noise has a direct or indirect influence on antenna performance along the feed or ground line of the antenna, even when the antenna is differently designed, there is a limitation on an improvement in its performance.
Although such noise may be blocked using a passive element or an L/C filer, in the case where the propagation pathway of noise cannot be exactly determined, design lead time may be increased, undesirably resulting in high cost.
Specifically, in the case where the propagation pathway of noise is unclear, many designs for blocking noise should be reexamined, and thus the lead time is increased, undesirably causing a problem of increasing the cost.
Furthermore, when the pathway of noise varies depending on changes in antenna design or a new noise source may be created, antenna performance may deteriorate as a result.